Just thinking: it would "only" take 4 PEMs, 4 Tesla motors (the electricity-to-motion converters, not the company!) and 12kWh of A123's (which can discharge at 60C) installed in a Veyron to match the Veyron's ICE and get to 250mph. Oh, and replace the gearbox with a 1:4 or so gear ratio on each wheel.
Considering all that, it's quite a radical racecar they used to get to 307mph, just 23% above the Veyron's top speed.